Abstract

Previous investigators have found that the kinetics of oxygen uptake (C02), carbon dioxide output (VCO2), and ventilation (VE) are considerably slower for upper body than for lower body exercise. We have shown that slow response kinetics are obtained for lower body exercise when the work rate engenders lactic acidosis. Since even low levels of upper body exercise produce lactic acidosis in most subjects, we sought to define upper body response kinetics during aerobic exercise by studying eight subjects who had trained extensively for arm-cranking tasks. Standing arm ergometer exercise was performed; VO2, VCO2, and VE were recorded breath-by-breath. From incremental exercise tests, VO2max averaged 3.9 L/min and anaerobic threshold (AT) averaged 1.9 L/min. Subjects then performed three transitions from rest to a sub-AT work rate (average, 67 W) and one transition from rest to a supra-AT work rate (average, 134 W). A single exponential model was fitted to each response time course to obtain a time constant (t) for each variable studied. The t following exercise onset for VO2, VCO2, and VE averaged 36, 42, and 39 seconds at the sub-AT work rate but were much longer (69, 63, and 96 seconds) at the supra-AT work rate. We conclude that ventilatory and gas exchange kinetics during aerobic work are not inherently slower for exercise predominantly involving the upper body than for lower body exercise. Like lower body exercise, work rates that are above the AT feature slow response kinetics for upper body exercise. Verf.-Referat